An online game is normally designed so that the player registers himself as a user to acquire an account, logs in using the acquired account, and then plays the game. The player can meet another player during the game via a chat in a lobby or the like. A friend function has been known that allows the player to register another player as a friend (or teammate) by performing given registration procedures.
The friend function is considered to be a function that links one player and a plurality of other (different) players (see JP-A-2011-110139 and JP-A-2011-206484, for example).